Refractory panel unit with hinge means and frangible portions



Nov. 18, 1969 w. M. CHARMAN, JR., ETAL 3,478,999

REFRACTORY PANEL UNIT WITH HINGE NEANS AND FRANGIBLE PORTIONS Filed April 29, 1968 5 SheetsSheet 1 FIG5 INVENTORS WALTER M. CHARMAA/JR.

G RGE J M/DDAUGHJJR.

NOV. 18, 1969 w CHARMAN, JR" ETAL 3,478,999

REFRACTORY PANEL UNIT WITH HINGE MEANS AND FRANGIBLE PORTIONS Filed April 29, 1968 3 Sheets-5heet K.

INVENTORS WALTER M CHARMAN,JK

$50265 J M/DDAUG/i JR.

Nov. 18, 1969 w, H RM JR ETAL 3,478,999

REFRACTORY PANEL UNIT WITH HINGE MEANS AND FRANGIBLE PORTIONS Filed April 29, 1968 3 Sheets-Sheet INVENTORS WA LTER M. CHARMAMJR GORGE J M/DDAuza/g J? ATTORNEYS United States Patent Int. Cl. B22d 7/10 U.S. Cl. 249-201 10 Claims ABSTRACT OF THE DISCLOSURE A two part insulating lining for a hot top comprised of a refractory panel insert unit and a bottom ring of the same type of material where the insert unit comprises a plurality of highly insulating refractory panels which are integrally connected 'by frangible refractory connecting portions. A wire mesh netting is embedded at least partially in the back of the panels and provides a hinge interconnection between the panels upon breaking of the frangible connecting portions. The entire insert unit is manufactured by making a slurry of sand, a resin binder, an inorganic fibrous material, and water, and depositing the slurry on a filter screen in a frame over a vacuum box, and embedding the wire netting in the layer of slurry. Applying a vacuum under the filter screen in the vacuum box effects removal of part of the water from the slurry and leaves a wet mat in which is embedded wire netting. The wet mat is then dried and hardened to form the highly insulating refractory panel insert unit. The ring is similarly manufactured.

This application is a continuation-in-part of copending application Serial No. 636,072, filed May 4, 1967.

The present invention relates to a hot top structure and a method of making the same and more particularly to a refractory panel insert unit having a plurality of interconnected panel sections which are relatively movable to form a tubular container at the upper end of an ingot mold to permit metal in a molten state to be fed to'the solidifying metal in the ingot mold to compensate for shrinkageof the metal during solidification thereof.

*In accordance with the present invention, there is provided a strong, easily shipped, stored, and handled wrapup panel insert unit, made of a relatively cheap refractory which is such a highly efficient insulator that a relatively thin lining of this material, say A to 1%" in thickness, is equivalent to the insulation provided by expensive insulating brick linings equal in density to such insert panels, but twice as thick, say 1 /2" to '2 /2, and can therefore be used to replace such thick expensive insulating brick linings, particularly in hot top casings, and permit the use of such wrap-up panel insert units in brickless hot top casings.

Since the wrap-up insert is inexpensive as compared to an insulating brick lining twice as thick, it can be used once and replaced, while an insulating brick lining of twice the thickness must be installed in the hot top casing, used repetitively and protected after each use to be justified economically.

The above wrap-up panel insert therefore provides a simple hot topping operation by eliminating the re-usable brick lining and the labor required to install and maintain such a lining. The simplicity of the resulting hot topping operation also results in a short hot top preparation time and increased hot top turnover and availability,

3,478,999 Patented Nov. 18, 1969 "ice so that more ingots can be produced with a smaller number of hot top casings from a smaller handling area.

The present invention provides an improved highly insulating refractory panel insert unit for hot topping which is lightweight but of strong construction so that it may be easily handled, shipped, and stored with a minimum of breakage. Even though the panel insert unit is structurally strong, the panels thereof may be readily moved relatively to form the hollow tubular container for use. Moreover, the unit is constructed so that the adjacent joint surfaces of the panels are obtained without grinding these joint surfaces, or otherwise separately operating on these joint surfaces of the panels. In fact, the entire insert unit is constructed by a method which includes a single vacuum molding operation and without handling of separate panels.

The highly insulating refractory insert unit is particularly adapted for use in a hot top casing without a ceramic lining supported at the upper end of an ingot mold, or for use without a hot top casing directly in the ingot mold. However, the highly insulating refractory insert of the present invention is also adapted for use when backed up by a hard dense fire-back or equivalent castable lining in a hot top casing.

The present invention further contemplates a new and improved highly insulating panel insert unit wherein the adjacent panels are connected by frangible integral connecting portions which are easily broken to allow the panels to be relatively moved to form the tubular container with the adjacent joint surfaces of the panels being moved into area contact with one another.

The present invention still further contemplates the provision of a new and improved highly insulating panel insert unit, as noted in the next preceding paragraph, and wherein the refractory panels and frangible connecting portions are made of the same refractory material and wherein a flexible hinge means extends between adjacent panels and interconnects the panels when the frangible connecting portions are broken.

The present invention further provides a new and improved highly insulating panel insert unit wherein the hinge means is a wire netting at least partially embedded in the refractory material forming the panels and the connecting portions.

The present invention also provides a new and improved lightweight insulating lining for protecting the interior of a metal hot top casing which is formed of a granular refractory material, a fibrous material preferably inorganic and a binder with the entire lining being comprised of the same material and made into two parts with one part comprising a bottom ring for protecting the underside of the casing and the other part comprising a unit for protecting the interior generally axially extending sides of the casing.

Also, the present invention provides a new and improved bottom ring of high heat insulating characteristics but which is lightweight and readily handled and is adapted to support a heat protective unit in the hot top.

In addition, the present invention provides a new and improved method for making a highly insulating panel insert unit, as defined in the preceding paragraphs, and which method includes a molding operation during which the flexible hinge means is substantially embedded within the refractory material and during which the panels and frangible panel connecting portions are shaped.

The present invention still further provides a new and improved panel insert unit adapted to be shipped flat and to be folded up to fit into a hollow hot top structure with the unit comprising corner panel sections which join panel sections which are disposed generally transversely of each other when in use, the corner panels being made up of a plurality of relatively movable subsections to adapt the corner panel section to a curved corner in the annular structure.

The present invention further provides a new and improved method for making a highly insulating panel insert unit of the kind defined in the preceding paragraphs, and which includes the steps of placing the flexible hinge backing, preferably a. flexible wire netting or screen on the filter screen of a vacuum box, placing a contoured molding frame shaped so as to form the refractory panels and panel connecting portions over the flexible wire netting and on the filter screen, pouring a refractory slurry into the contoured molding frame, and partially vacuum dewatering the refractory slurry to form or mold a wet refractory mat, removing the contour molding frame from the Wet mat panels, and drying the wetness out of and hardening the mat by oven baking or other means to form the highly insulating panel insert unit.

The present invention additionally provides a new and improved method for making a panel insert unit as defined in the next preceding paragraph, and wherein the grooves which define the joint surfaces of the panels are formed by positioning bars in the molding frame and which are spaced from the vacuum filter screen, and the molding method is carried out by creating a vacuum beneath the filter screen to remove most of the liquid from the slurry after the slurry is poured into the mold and flows beneath the bars and around the wire netting to provide the frangible portions integrally interconnecting the adjacent panels.

The present invention further resides in various novel constructions and arrangement of parts, and further advantages of the present invention will be apparent to those skilled in the art to which it relates and from the following detailed description of the illustrated embodiment thereof made with reference to the accompanying drawing a part of this specification and in which similar reference numerals are employed to designate corresponding parts throughout the several views, and in which:

FIG. 1 is a fragmentary view, partly in elevation and partly in section, of a hot top embodying the present invention and taken approximately along line 11 of FIG. 2 and shown mounted in the open upper end of an ingot mold;

FIG. 2 is a fragmentary sectional view taken approximately along line 2-2 of FIG. 1;

FIG. 3 is a view of a panel insert unit embodying the present invention and illustrates the insert unit in its molded and baked condition ready for packaging and shipping;

FIGS. 4 and 4a are enlarged fragmentary sectional views of the panel insert unit shown in FIG. 3;

FIG. 5 is a fragmentary vertical sectional view showing an insert unit of the present invention positioned in the open upper end of an ingot mold;

FIG. 6 is a fragmentary top plan view of the bottom ring used with the insert unit;

FIG. 7 is a fragmentary and somewhat schematic top plan view of an apparatus for use in making the panel insert unit shown in FIG. 3;

FIG. 8 is an enlarged fragmentary longitudinal crosssectional view of the apparatus shown in FIG. 7;

FIG. 9 is a view of a modified hot top casing and modified insert unit positioned therein;

FIG. 10 is a fragmentary front side view of the insert unit of FIG. 9; and

FIG. 11 is a sectional view taken along line 11-11 of FIG. 10.

The present invention provides a novel panel insert unit and method of making the same, and more particularly provides a novel preformed panel insert unit having a plurality of integrally connected panels or panel sections 10a, 10b which are relatively movable to provide a multisided tubular container at the upper end of an ingot mold to hold a mass of metal in a molten state above the ingot mold to compensate for shrinkage of the metal in the mold during solidification thereof. Although the preformed panel insert unit 10 can be embodied in or is susceptible for use with various types of hot top constructions, it is particularly useful when folded and inserted in a hot top casing, to form a highly insulating hot top A.

The hot top A is adapted to be mounted in the open upper end of an ingot mold 12 and insofar as the metal casing 11 and its manner of use are concerned, is convention-a1. As best shown in FIG. 1, the metal casing 11 is of a one-piece construction having a central opening 13, although the casing can be made in two pieces and fastened together. The opening or internal cavity 13 is tapered so as to be larger at the bottom than at the top thereof. It will, of course, be understood that the opening 13 could be non-tapered and be of any suitable configuration, such as round or oval, if desired.

The panel insert unit 10 is adapted to be folded to form a multi-sided tubular container or inner hot top lining having sides shaped complementary to and corresponding in number to the sides defining the opening 13 in the metal casing 11. In the illustrated embodiment, the opening 13 in the metal casing has eight sides and the panel insert unit 10 has eight alternatively spaced side and corner panels 10a and 10b so as to form an eight sided hollow figure shaped complementary with the eight sided opening 13. The panel unit 10, when folded to form the inner hot top lining is adapted to be inserted into the opening 13 of the metal casing 11. The panel insert unit is held against the interior sides of the casing 11 by the taper of the insert against the taper of the casing, and is supported by the bottom ring.

After the panel insert unit 10 is positioned in the metal casing 11, a refractory bottom ring 16 is placed on the lower end of the hot top, and in a manner and for reasons Well known to those skilled in the art. The refractory bottom ring 16 has an upper surface that engages the lower edge of the panel insert unit 10 to aid in supporting the latter within the metal casing 11 and to prevent molten steel getting behind the panel insert. A wiper strip 18 is positioned on the bottom ring 16 and which is engageable With the sides defining the opening at the upper end of the mold 12 for reasons well known to those skilled in the art. The refractory bottom ring 16 and the wiper strip 18 are adapted to be secured to the casing 11 in any suitable or conventional manner, such as by clips adapted to be received in notches 17 in the interior surface of the ring.

When the hot top A thus equipped is used for a pouring operation, it is positioned a predetermined distance in the upper open end of an ingot mold 12 and initially held in such position by suitable blocks (not shown). After the pouring of the molten metal into the mold 12 and the hot top A, the blocks are knocked out or destroyed and thereafter the hot top rests or floats on the solidifying ingot. The hot top contains a molten mass of metal some of which is fed to the ingot in the mold to compensate for shrinkage of the metal during the solidification.

The insulating bottom ring further protects the bottom end of the casting, and most important of all, provides a highly insulating heat barrier between the molten steel and the hot top casing at the critical lower tapered opening or junction of the hot top, minimizing the chil effect of the hot top casing at this critical point and prevents a steel bridge from forming at this point before the metal in the hot top has completely filled the shrinkage in the ingot below the throat or junction of the hot top and ingot mold.

The panels or panel sections 10a, 10b of the panel insert unit 10 are preferably made from a highly insulating refractory material and are disposed in a side-by-side relationship, and with the adjacent panels being integrally connected by refractory portions 22 of reduced thickness as compared to the thickness of the panels 10a, 10b

proper. The panels are preferably to 1 /2" in thickness. The panels have substantially planar front and back faces 23, 24 which respectively are adapted to face toward and away from the interior of the hollow inner hot top lining when the unit is folded. The panels 10a, 10b, as viewed in FIG. 3, have planar top and bottom edge surfaces 27, 28 joining and extending transversely of the front and back faces 23, 24 and planar adjacent side edge surfaces 30, 31 joining the front face and extending toward the back face, but terminating at a location spaced from the back face 24. The top and bottom edge surfaces 27, 28 are preferably tapered so as to form with the front face 23 an obtuse included angle therebetween.

The adjacent side edge surfaces 30, 31 of adjacent panels 10a, 1011 are spaced from and face one another and are tapered so as to form with the front faces 23 an obtuse included angle therebetween. The adjacent side edge surfaces 30, 31 are planar and tapered toward each other so as to join one another at a location intermediate the front and back faces 23, 24 of the panels so as to define grooves 32 whose bottoms 33 are spaced from the back face 24 of the panels preferably approximately 7 from the back face of the panels. The grooves 32 are V-shaped and the adjacent side edge surfaces 30', 31 define an included angle therebetween. The angle of the groove will vary depending upon the number of panels in the insert unit and the angular distance through which the panels must move to conform to the opening in which they are to be inserted. For example, if four panels are in the insert unit and the unit is to form a complete lining, the angle of the groove would be approximately 90 degrees. In the illustrated embodiment of FIGS. 1-4, the angle is approximately degrees.

The refractory portions 22 integrally connecting the adjacent panels 10a, 10b extend between the bottoms 33 of the grooves 32 and the back face 24 of the panels. These portions 22 are frangible and break substantially along the bottom 33 of the V-shaped grooves 32 when the panels 10a, 10b are relatively moved to form the hollow lining, as will be hereinafter more fully apparent.

The panels 10a, 10b of the preformed insert unit 10 are also hingedly connected together by a flexible backing or hinge means 40 secured thereto and preferably substantially embedded therein. The hinge means 40 could be of any suitable construction and formed from any suitable material which has suflicient strength to support the respective panels when the frangible portions 22 are broken. Preferably, the hinge means is a flexible wire netting or screen. The flexible wire netting or screen is preferably completely embedded within the material at a location spaced rearwardly from the bottom 33 of the grooves 32, and intermediate the bottom 33 of the grooves 32 and the back face 24 of the panels 10a, 10b. The thickness of the wires forming the wire screen is somewhat exaggerated in the drawings for illustrative purposes. 3

The materials and the compositions from which the rings and panels are made may vary within certain limits, but where the highly insulating insert unit is to be used against a cast iron casing or in an ingot mold, as shOWn in the drawings, the insert unit is preferably made of a material which includes a granular refractory filler, such as silica flour of such particle size as to substantial-ly all be through 200 mesh U.S. sieve, a heatcollapsible binder, and an organic fibrous material such as wood and paper pulp and/ or inorganic fibrous material such as mineral wool or asbestos, or a synthetic inorganic fibrous material. The fibrous material is preferably an asbestos material or a synthetic fiber. A material of this type is disclosed in United States Patent No.

The material may be essentially comprised of the following:

Ingredient: Range (parts by wt.) Granular refractory filler 79-90 Binder 5-10 Asbestos having less than 6% water 5-10 Organic fibrous material 2 The asbestos material is preferably amosite asbestos and may include a portion of chrysotile asbestos but in quantities insufficient to introduce an objectionable water content. For example, the asbestos in the ring may comprise 25% chrysotile asbestos. Crocidolite, anthophyllite and tremolite are other examples of low water content asbestos which may be used. Also, other refractory fillers such as diatomaceous earth, magnesia, alumina, or forsterite are usable.

The fine port structure created in the manufacture of the panels make the panels highly insulating. The high insulating property of the panels can be expressed by the thermal conductivity or K factor of the material. The K factor is, as is well known in the art, the amount of heat in B.t.u.s which will flow through 1" thick 1 sq. ft. area in one hour per degree F. difference between the hot and cold sides or faces of the panel. The K factor varies with the average or means temperature between the hot and cold faces of the material. The present panels are highly insulating since they have a K factor of less than 1.5 determined for an average or mean temperature range of 1000 degrees F. to 1750 degrees F. This, of course, means that less than 1.5 B.t.u.s are lost by conduction through 1 sq. ft. of a 1" thick panel in one hour for each degree F. difference between the hot and cold faces of the panel. The relatively low K factor indicates that the panels are highly insulating and particularly adapted for use in a hot top casing without a ceramic lining or directly in an ingot mold.

The panel unit 10 is preferably formed by a vacuum or pressure wet molding operation during which the flexible wire netting is immersed in the aqueous slurry therein and in which the panels 10a, 1% are formed in a sideby-side open, unfolded position, as shown in FIG. 3, and in a manner to be hereinafter more fully described.

The panel insert unit is adapted to be folded from its unfolded position shown in FIG. 3 to a position in which the adjacent side and corner panels 10a, 10b are angularly related to form a tubular container for insertion into the opening 13 of the metal casing 11 by grasping the adjacent panels 10a, 10b and bending and stretching the flexible netting 40 at and along the frangible portions 22 between the panels to an angle necessary to bring the adjacent side edge surfaces 30, 31 of the panels into engagement with one another. During the folding movement of the adjacent panels 10a, 10b, the frangible portion 22 therebetween will break to allow the flexible screen 40 to bend so that the adjacent side edge surfaces 30, 31 of the panels 10a, 10b properly mate to form the tubular container. The flexible netting holds the panels together after the frangible portion 22 are broken. The preformed insert unit 10, when folded to form the inner hot top lining, then is inserted into the opening 13 in the top of the metal casing. The bottom ring 16 and the wiper strip 18 are then secured in place and the hot top A is positioned in the opening at the upper end of the mold. The molten metal to form the ingot is then poured through the hollow opening 13 in the hot top A and the hot top is filled to the level desired. The panel insert unit 10 makes a highly insulating container and provides that some of the molten metal in the hot top A will feed by gravity to the ingot in the mold to compensate for shrinkage of the metal during solidification.

It has been found that by providing the frangible portions 22 for integrally connecting the adjacent panels 10a, 10b, a strong flat construction is achieved which may be readily shipped without significant breakage, and yet when the adjacent panels are folded they form a tubular container backed up by a hot top casing or mold wall. By embedding the flexible wire netting 40 in the insert unit 10' closely adjacent the bottom of the grooves, but between the bottom of the grooves and the back faces 24 of the panels, the adjacent panels can be folded such that their adjacent joint surfaces mate along their entire length. By providing reasonably tight joints between the adjacent panels, metal leakage through the joints and behind the panels is minimized. Additionally, it has been found by substantially embedding the flexible Wire netting between the back faces of the panel and the bottoms of the grooves that the panels, being reinforced by wire netting, can withstand rough handling, and the inserts will hold together and be usable even if panels are cracked during shipment, storage, and handling.

It should be noted that since the central opening 13 of casing 11 is tapered, the panel insert unit 10, is designed so that when folded, it forms a generally trapezoidal tubular container. The insert unit 10, when in its flat unfolded condition, as illustrated in FIG. 3, is segmented and somewhat curved, and with the panels 10a being of a trapezoidal shape and panels 10b being rectangularly shaped. If the central opening of the casing is not tapered but is formed by parallel sides, then the insert unit in its flat condition would be in the form of a rectangle and, when folded, would form a generally cylindrical tubular container.

FIG. shows another way in which the panel insert unit can be employed to form a hot top. The panel insert unit 10 is there shown as being inserted down into and attached directly to the open upper end of an ingot mold 50. The ingot mold 50, as shown in FIG. 5 is of the conventionally known, big-end-down type of ingot mold having a downwardly tapered central opening 52. A big-end-down type of ingot mold is one in which the central opening 52 is tapered so as to be larger at the bottom than at the top thereof. It will, of course, be understood that the provisions of the present invention are also applicable to the big-end-up type of mold and to molds having different contours.

The panel insert unit 10, when folded to form a tubular container or form whose sides are complementary to the sides of the opening 52, is adapted to be inserted into the opening of the mold 50' and attached to or held against the interior sides defining the opening 52 by any suitable or conventional means to form a hot top. After the insert unit 10 is in place, molten metal to form the ingot can then be poured through the tubular container to the level desired to provide that some of the molten metal at the upper end of the ingot in the mold will feed downward to compensate for shrinkage of the metal in the solidifying ingot.

In the preferred embodiment, the lining for protecting the casing includes the bottom ring 16 which is formed as a separate part but is of the same type of material as the unit 10. This material is relatively light and highly insulating and the ring thereof is quite easily handled. Moreover, we have found that improved metallurgical results are achieved by the use of the ring of this invention as compared to the conventional hot top bottom rings now used in the industry, which rings are formed essentially of silica and a sodium silicate binder and are much heavier and less insulating.

As illustrated in FIG. 6, the ring has an annular outer flange portion 16a which runs along the underside of the casing adjacent its exterior side and upwardly and in clined, frustoconical portion 16b rising from the smaller dimension of the annular portion 16a and terminating in a generally horizontal top surface 16c, and a generally vertical inner surface 16d extending downwardly for a short distance from the inner edge of the top surface 16c. The inclined portion 16b follows the taper of the casing 11 at its bottom end and has an external configuration complementary to the tapered portion of the casing. The

" surface 16d of the ring extends inwardly from the interior axially extending sides of the casing 11 and forms a support for the insert unit 10. The ring also has a wire netting 16e embedded therein with the plane of the netting extending around the central opening in the'ring. The netting preferably extends entirely around the opening.

The bottom ring 16 not only provides improved metallurgical characteristics but the combination with the unit 10 provides a lightweight insulating lining for all the surfaces of the casing 11 which are to be protected against molten metal but yet provides a complete lightweight lining which can readily be handled and shippedin a minimum amount of space. Y

A novel and economical method may be utilized for making the panel insert unit and ring. The method, in general, includes a one-step molding operation for each the unit and ring in which the panels 10a,"10b and the frangible sections22 are shaped as an integral unit and the flexible wire screen is embedded within the refractory material. The various steps in carrying out the method of the present invention will be described with reference to the description of an apparatus 55, schematically shown in FIGS. 6 and 7, for carrying out the method.

The apparatus for carrying out the method of'the present invention comprises a vacuum box which is an open top box of the desired shape and which has a horizontally disposed vacuum screen 61 backed up by a strong grid 61a' extending thereacross at its upper'end. The box 60 is provided with an upwardly facing peripherally extending supporting ledge 62 on which the vacuum screen 61 and grid 61a is supported. The vacuum screen 61 defines with the sides and bottom of the box 60 a vacuum chamber 63 located beneath the vacuum screen 61. The vacuum chamber 63 is adapted to be connected with a suitable vacuum source to provide or create a vacuum in the chamber 63 and the presence of the vacuum in the chamber 63 is designated generally by the arrow 64.

The contoured molding frame comprises an outer frame part 71 shaped so as to provide the outer peripheral configuration of the panel insert unit 10 when in its flat position, as shown in FIG. 3. A plurality of spaced bar members 72 are suitably secured to and extend transversely between the upper and lower generally longitudinal extending portions of the outer frame part 71, as viewed in FIG. 7. The bars 72 are employed to form the grooves 32 in the panel unit 10 and are spaced and disposed relative to each other and the outer fame 71 so as to define with the outer frame 71 the configuration of the respective panels 10a, 10b to be molded.

As best shown in FIG. 7, the bars are V-sh'ap'e d to form the V-shaped grooves 32 in the panel unit 10 and the inner vertically extending sides 75 of the outer frame part 71 are suitably contoured or tapered to provide. the free side edge surfaces 30 and 31 of the two 'endmost panels. The top and bottom end surfaces ,atieach panel have tapered surfaces formed by corresponding surfaces of frame 71. The outer frame part 71 has a planar bottom surface 76 which is placed directly 'onto the vacuum screen 61 and the bars 72 have their lowermost portions 78 located or spaced above the plane, of the {bottom surface 76 of the outer frame part 71, and -thus located above the vacuum screen 61, and for, reasons to be hereinafter more fully described. I

In carrying out the steps of the method, the flexible wire netting 40 is placed directly. on the vacuum .screen 61 and then a contoured molding frame 70 movablerelative to the box 60 is placed or positioned ontop of -the vacuum screen 61.

After the contoured molding frame 7!} has 'be enplaced onto the vacuum screen 61. to form a mold,-this mold is filled with slurry of a suitable composition, such as the composition disclosed in the aforementioned Patent No. 3,733,047. The slurry covers the vacuum screen 61 and surrounds and flows underneath the bar members 72 to provide the frangible portions 22 and surrounds the wire netting to substantially embed the latter within the slurry. With the creation of the vacuum 64 the slurry is partially de-watered to leave a wet mat and then the contoured molding frame 70 is moved upwardly relative to the vacuum box 60 to remove the same from the wet mat which will subsequently become the panel insert unit 10.

By using the bar members 72 whose bottommost portions are spaced upwardly from the vacuum screen 61 so that the slurry flows beneath the bar members, accurate spacing between the adjacent joint surfaces 30, 31 of the adjacent panels is achieved, which, in turn, enables mitered joints to be effected when the panel insert unit is folded to form a tubular container and a workable fit of the insert into the hot top casing, or ingot mold. Moreover, it has been found that the employment of this molding method enables the units to be more rapidly produced due to the minimizing of air leakage through the slurry around the bottom and sides of the bar members and, thus, helps to prevent loss of vacuum around the panel perimeters and enables the units to be produced at relatively low cost. Additionally, by substantially embedding the flexible screen within the refractory panel insert, loosening of the panels from the screen and breakage of the panels is minimized or eliminated.

The bottom ring may be molded in a similar manner; that is, by partially de-watering a refractory slurry of suitable composition against a screen formed to mold the ring to the desired shape, by forcing the slurry against the shaped screen by use of either a pressure or vacuum system or combination of both.

The present invention also contemplates the provision of an insert unit which is adapted to be used with a hot top casing which has rounded corners as shown in FIG. 9. The hot top casing shown in FIG. 9 has an opening defined by planar sides 80 which are joined by arcuate corners 81.

The insert unit is comprised of panel sections 84 which correspond respectively to the planar sides of the hot top and corner panel sections 85 each of which corresponds to and is adapted to cover a respective one of the arcuate corners 81. In the embodiment of FIG. 9, a corner panel section 85 is disposed between each of the side panel sections 84 and the construction of the panel insert unit is essentially the same as the first described embodiment except for the corner panel sections 85 which are particularly adapted for use with an arcuate corner. Each of the corner panel sections 85 has a plurality of V-shaped grooves 86 molded in the front side thereof. The grooves 86 extend from the top to the bottom of the insert unit and subdivide the corner panel section into a plurality of subsections 87 which extend the height of the panel and which are movable angularly with respect to each other to fit around a corner. In a tapered hot top structure, the grooves will converge somewhat from the bottom to the top of the insert as in the case of the large panel sections. The grooves 86 are formed in the same manner as the grooves 32 of the first described embodi ment to provide for the relative angular movement between the subsections 86 in the same manner as the relative angular movement of the panel sections 10 a, 10b of the first described embodiment is provided thereby enabling the corner panel section to be shipped flat and when used for the corner panel subsections to be moved relative to each other and to the side panels to fit the opening. The movement of the panel sections, including the subsections relative to each other will move adjacent panel sections into edge-abutting relationship. The back sides of the panel subsections of each corner panel each lie along a short chord of the corresponding arcuate corner and provide a satisfactory fit against the arcuate corner. The member and depth of the grooves 86 and the included angle of the sides in the grooves of each corner section depends on the radius of curvature of the arcuate corner of the casing. The V-grooves in each corner panel section are such that the sides of each groove, i.e. joint surfaces 90, mate with area contact when the corner panel section is folded to fit the arcuate corner it is to protect. In view of the fact that the construction and operation of the subsections of the corner panel sections are the same as the construction and operation of the adjacent panels of the first described embodiment and in view of the fact that the corner panel sections are molded to the adjacent side panel sections in the same manner as in the first described embodiment, the construction, method of molding and operation will not be repeated. It is to be understood that the corner panel sections are molded with the flexible interconnecting ma terial located adjacent the back side of the corner sections and that it extends between the subsections between the bottoms of the V-grooves and the back side of the insert unit.

It will be understood by those skilled in the art that the frangible portions 22 may be broken prior to the actual use of the insert in a casing. In such a case, the frangible portion 22 is advantageous in producing a commercially acceptable one-piece unit.

While the various parts of the preferred embodiments have been described in detail other equivalent elements may be utilized.

What is claimed is:

1. An insulating lining comprising a highly insulating refractory panel insert unit for use in lining a metal casing, said unit having front faces and a rear face remote therefrom and comprising a plurality of panel sections having front faces for forming adjacent interior faces of a hot top opening, said panel sections having a formed joint surface facing each adjacent panel section with the joint surfaces each being in a plane defining an obtuse included angle with the front face of the panel section, frangible portions of refractory material integrally molded with said panel sections extending between said panel sections adjacent the rear side of the unit, said frangible portions providing for relative angular movement of said panel sections after molding from an opened out shipping position where facing joint surfaces of adjacent refractory panel sections are spaced to a position where the spaced joint surfaces of adjacent refractory panels are in substantial contact to position the refractory panels to form interior faces of the hot top and to block leakage of molten metal behind the panels, said insert unit being a one-piece vacuum or pressure molded unit and said panel sections being made of a material comprising a granular refractory material, a heat-destructible binder, and a fibrous material, and flexible non-frangible hinge means embedded in said panel sections and having hinge portions extending between and inter-connecting said panel sections, said hinge portions being substantially completely imbedded in said frangible portions when molded and said hinge means being disposed at and inwardly of the plane of the rear face of said panel sections.

2. A highly insulating refractory panel insert unit as defined in claim 1 wherein said panel sections have a K factor of less than 1.5 determined at a mean temperature of the opposite faces ranging between 1750 degrees and 1000 degrees F.

3. A highly insulating refractory panel insert unit as defined in claim 1 and wherein at least one of the refractory panel sections of said panel insert are vertically tapered.

4. A highly insulating refractory panel insert unit as defined in claim '1 wherein said hinge means comprises a fiexible wire netting.

5. A panel insert unit for use in hot topping, said unit having front faces and a rear face remote therefrom and comprising a plurality of panel sections having front faces for forming adjacent interior faces of a tubular container, said panel sections having joint surfaces facing each adjacent panel section with the joint surfaces each being in a plane defining an obtuse included angle with the front face of the panel section, material molded integrally to said panel sections extending between said panel sections adjacent the rear side of the unit, said molded material providing frangible portions to provide for relative angular movement of said panel sections after molding from an opened out shipping position where facing joint surfaces of adjacent panel sections are spaced to a position where the spaced joint surfaces of adjacent panels are in substantial contact to position the panels to form interior faces of the tubular container and to block leakage of molten metal behind the panels said material between said panel sections breaking upon said relative angular movement, and flexible non-frangible hinge means imbedded in said panel sections and having hinge portions extending between and inter-connecting said panel *sections, said hinge portions being substantially ompletely imbedded in said frangible portions as molded and said hinge means being disposed at and inwardly of; the plane of the rear face of said panel sections.

6. A panel insert unit of refractory material for use in hot topping and for insertion 'into the central opening of an annular metal structure at the top of an ingot mold with the structure having generally planar sides joined by arcuate corners to be protected by said unit, said unit having a front side to form the faces of the opening through said structure and a back side extending generally parallel to said front side and a plurality of formed grooves opening from the front side thereof toward the back side to define a plurality of panel sections comprising first and second panel sections corresponding to first and second sides of said structure and a plurality of third panel sections defining a corner panel for fitting an arcuate corner of said structure and interconnecting said first panel section and said second panel section, the sides of each of said grooves'converging outwardly and providing joint surfaces on adjacent panel sections which face each other, the depth of said grooves being less than the distance between said front and back sides and the refractory material portions between said grooves and the back side being frangible and providing for relative angular movement of said panel sections from an'opened out shipping position where facing joint surfaces of adjacent panel sections are spaced to a folded-up position where the joint surfaces of adjacent panels are in contact for a substantial depth to position the panel sections to form interior faces of an opening through said structure, and flexible nonfrangible means substantially completely embedded in said frangible portions when molded and being disposed at and inwardly of the plane of said back side and interconnecting said panel sections upon the breaking of said frangible material.

7. A panel insert unit as defined in'claim 6 wherein said unit is a pressure molded one-piece refractory material comprised essentially of a fibrous material, a re fractory filler for said fibrous material and an organic binder. ,9

8. An insert unit as defined in claim 6 wherein said flexiblenonfrangi-ble means is a wire netting.

9. An insulating lining comprising a highly insulating refractory panel insert unit for use in lining a metal casing, said unit having front faces and a rear face remote therefrom and comprising a plurality of panel sections having front faces for forming adjacent interior faces of 'a hot top opening, said panel sections having a joint surface facing each adjacent panel section with the joint surfaces each being in a plane defining an obtuse included angle with the front face of the panel section, frangible refractory material integrally molded with said panel sections and extending between said panel sections adjacent the rear side of the unit and flexible nonfrangible hinge means imbedded in said panel sections and having hinge portions extending between and inter-connecting said panel sections, said hinge portions being substantially completely imbedded in said frangible portions as molded and said hinge means being disposed at and inwardly of the plane of the rear face of said panel sections, said refractory material being frangibleto provide for relative angular movement of said panel sections from an opened our shipping position where facing joint surfaces of adjacent refractory panel sections are spaced to a position where the spaced joint surfaces of adjacent refractory panels are in substantial contact to position the refractory to form interior faces of the hot top and to block leakage of molten metal behind the panels, said refractory material between said panel sections breaking upon relative angular movement, said insert unit being a one-piece pressure molded unit and said panel sections being made of a material comprising a granular refractory material, a heat-destructible binder, and a fibrous material, and a bottom ring for supporting said unit and for protecting the bottom end of the metal casing said ring being comprised of a material comprising a granular refractory material, a heat-destructible binder, and a fibrous material.

10. An insulating lining as defined in claim 9 wherein a wire netting is embedded in said material of said ring with the plane of said netting extending around the opening in said ring.

References Cited UNITED STATES PATENTS 1,428,733 9/1922 Wilson 249-52 2,054,499 9/1936 Florman.

2,361,386 10/1944 Eayrs 249-197 X 3,063,111 11/1962 Anthony 249202 3,216,689 11/1965 Carpenter 24920l 1,792,868 2/1931 Ramage 249201 I. SPENCER QVERHOLSER, Primary Examiner ROBERT D. BALDWIN, Assistant Examiner US. Cl. X.R. 249-52 

